JP2010251591A - Thin film transistor and method of manufacturing the thin film transistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film transistor which can be formed at low temperature through simple processes, is superior in mobility and an on/off ratio, and is improved with respect to shifting to minus side of rising voltage, S value deterioration, and performance variation between elements to have high stability, and to provide a method of manufacturing the thin film transistor. <P>SOLUTION: The thin film transistor has a gate electrode 104 on a substrate 106, a gate insulating layer 105, a source electrode 102, a drain electrode 103, and a semiconductor layer 101. In the thin film transistor, the semiconductor layer 101 includes an oxide semiconductor formed by coating, and a layer 107 containing a fluorine compound is provided between the gate electrode 104 and the semiconductor layer 101. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a field effect thin film transistor (hereinafter also referred to as a thin film transistor element or an element) using a metal oxide semiconductor and a method for manufacturing the thin film transistor.

  A field effect thin film transistor (TFT) using a thin film such as amorphous silicon formed on a glass substrate and using it as an active layer, an active matrix circuit using these, and the like are well known.

  However, since TFTs using amorphous silicon have low carrier mobility and unstable characteristics during continuous driving, a stable thin film transistor with high carrier mobility is required for use in an organic EL active matrix circuit or the like. It has been demanded. A TFT using a polysilicon thin film has been developed as a high-mobility TFT, but the manufacturing process is complicated, such as the need for laser annealing that requires high-precision control, and performance variations between elements are also a problem. It has become. A TFT using an organic semiconductor is well known as a TFT to which a simple manufacturing process can be applied. However, since the carrier mobility is low, the performance deterioration during continuous driving and the variation between elements are large, an organic EL active matrix circuit. It has been found that it is insufficient for use in, for example. In recent years, TFTs using metal oxide semiconductors have been actively developed as TFTs that can be applied with simple manufacturing processes, have high stability and carrier mobility during continuous driving, and have low element-to-element variation and high mobility. Has been done.

  In particular, it has been found that an amorphous metal oxide having a composition of In—Ga—Zn—O is excellent as a semiconductor of a thin film transistor (see, for example, Patent Documents 1 to 3).

  Furthermore, a method for forming an oxide semiconductor layer by a solution process that can be easily formed at a low temperature and under atmospheric pressure is also disclosed (see, for example, Patent Document 4). However, many of these methods require high-temperature baking at 400 ° C. or higher in order to function as a semiconductor, and it is difficult to say that these methods can be applied to resin substrates.

  Further, as problems specific to a transistor having an oxide semiconductor layer formed by a solution process, S representing the shift of the rising voltage (Von) to the negative side in the transistor characteristics and the sharpness of the rising from the off current to the on current. It has been found by the inventors' investigation that the deterioration and variation of the value are problems.

JP 2006-165527 A JP 2006-165528 A JP 2007-73705 A JP 2001-244464 A

  The present invention has been made in view of the above problems, and an object of the present invention is to be formed by a simple process at a low temperature, excellent in mobility and on / off ratio, and further to the negative side of the rising voltage. It is an object of the present invention to provide a highly stable thin film transistor in which shift, S value deterioration, and performance variation between elements are improved, and a method of manufacturing the thin film transistor.

1. In a thin film transistor having a gate electrode, a gate insulating layer, a source electrode, a drain electrode, and a semiconductor layer on a substrate,
The semiconductor layer is made of an oxide semiconductor formed by coating,
A thin film transistor, wherein a fluorine compound-containing layer is provided between the gate electrode and the semiconductor layer.

  2. 2. The thin film transistor according to 1 above, wherein the fluorine compound-containing layer is provided between the gate insulating layer and the semiconductor layer.

  3. 2. The thin film transistor according to 1 above, wherein the fluorine compound-containing layer is provided in the gate insulating layer.

  4). 2. The thin film transistor according to 1 above, wherein the fluorine compound-containing layer is provided between the gate electrode and the gate insulating layer.

  5. 5. The thin film transistor according to any one of 1 to 4, wherein the fluorine compound-containing layer comprises a fluorine-based resin.

  6). 6. The thin film transistor according to any one of 1 to 5, wherein the oxide semiconductor is made of an oxide semiconductor containing zinc or indium.

  7). 7. The thin film transistor according to 6, wherein the oxide semiconductor is an oxide semiconductor containing an oxide containing zinc and indium, an oxide containing zinc and gallium, or an oxide containing indium and gallium. .

  8). 7. The thin film transistor according to 6 above, wherein the oxide semiconductor is an oxide semiconductor containing an oxide made of zinc, indium and gallium, or an oxide made of indium and gallium.

  9. 9. The thin film transistor according to any one of 1 to 8, wherein the semiconductor layer is formed of a film formed by a solution process using a precursor of an oxide semiconductor.

  10. 10. The thin film transistor according to any one of 1 to 9 above, wherein the semiconductor layer is a film formed by irradiating a film obtained by applying a precursor of an oxide semiconductor with microwave energy. .

  11. A method for producing a thin film transistor, comprising producing the thin film transistor according to any one of items 11.1 to 10.

  According to the present invention, it can be formed by a simple process at a low temperature, has excellent mobility and on / off ratio, and further has improved the negative voltage shift of the rising voltage, S value deterioration, and performance variation between elements. A highly stable thin film transistor and a method for manufacturing the thin film transistor can be provided.

It is a figure which shows the typical element structure of a thin-film transistor element. It is a schematic equivalent circuit diagram showing an example of a thin film transistor sheet in which a plurality of thin film transistor elements are arranged. It is a figure which shows the structure of the thin-film transistor element mentioned as an example in an Example.

  The best mode for carrying out the present invention will be described below, but the present invention is not limited thereto.

The present invention relates to a thin film transistor having a gate electrode, a gate insulating layer, a source electrode, a drain electrode, and a semiconductor layer on a substrate.
The semiconductor layer is made of an oxide semiconductor formed by coating,
A fluorine compound-containing layer is provided between the gate electrode and the semiconductor layer.

  Hereinafter, the present invention and its components will be described in detail.

(Fluorine compound-containing layer)
The fluorine compound-containing layer in the present invention is a layer comprising a compound containing a fluorine atom, a layer comprising a low molecular compound containing a fluorine atom or a layer comprising a low molecular compound containing a fluorine atom, Alternatively, it is a layer made of a fluorine resin or a layer containing a fluorine resin.

  The layer made of a low molecular compound containing fluorine atoms or the layer containing a low molecular compound containing fluorine atoms is subjected to surface treatment on a gate insulating layer (also referred to as a gate insulating film) made of, for example, silicon oxide. For example, self-assembled monolayers (also known as SAMs) using silane compounds and alkylsilazanes having a fluorine atom-containing alkyl group (fluoroalkyl group) or perfluoroalkyl group, which are generally known as agents. Can be formed. Specific examples of compounds capable of forming SAM on the gate insulating film are shown below, but the present invention is not limited thereto.

(Heptadecafluoro-1,1,2,2-tetrahydrodecyl) trichlorosilane (Heptadecafluoro-1,1,2,2-tetrahydrodecyl) triethoxysilane (Heptadecafluoro-1,1,2,2- Tetrahydrodecyl) trimethoxysilane (heptadecafluoro-1,1,2,2-tetrahydrodecyl) dimethylchlorosilane (tridecafluoro-1,1,2,2-tetrahydrooctyl) trichlorosilane (tridecafluoro-1,1 , 2,2-tetrahydrooctyl) triethoxysilane (tridecafluoro-1,1,2,2-tetrahydrooctyl) methyldichlorosilane perfluorododecyl-1H, 1H, 2H, 2H-triethoxysilane (3,3, 3-trifluoropropyl) trichlorosilane (3,3,3 Trifluoropropyl) trimethoxysilane (Shin-Etsu Chemical Co., Ltd. KBM7103)
Bis (trifluoropropyl) tetramethyldisilazane (3-heptafluoroisopropoxy) propyltrichlorosilane pentafluorophenyltriethoxysilane pentafluorophenyldimethylchlorosilane pentafluorophenylpropyltrichlorosilane pentafluorophenylpropyltrimethoxysilane 1,8-bis (trichloro Silylethylhexadecafluorooctane These above-mentioned compounds are available as products from Shin-Etsu Chemical Co., Ltd.

  In addition, as the fluorine compound-containing layer in the present invention, a fluorine resin that can be easily formed into a film by coating or the like can be preferably used for the layer made of the fluorine resin or the layer containing the fluorine resin. Examples of the fluororesin used in the present invention include perfluoropolyether materials, fluorinated monocyclic polymers, polytetrafluoroethylene, tetrafluoroethylene-perfluorovinylether copolymers, and tetrafluoroethylene-hexafluoropropylene. Copolymers, tetrafluoroethylene-ethylene copolymers, polyvinylidene fluoride, ethylene trifluoride chloride, vinylidene fluoride-vinylidene trifluoride copolymers and the like are exemplified, but the present invention is limited to these. It is not a thing.

These above-mentioned compounds are available as products such as Von Bridendol DOL-4000 (manufactured by Augmond) and Cytop (manufactured by Asahi Glass).
(Position of fluorine compound-containing layer)
The present invention relates to a thin film transistor having a gate electrode, a gate insulating layer, a source electrode, a drain electrode, and a semiconductor layer on a substrate, wherein the semiconductor layer is formed of an oxide semiconductor formed by coating, and the fluorine compound-containing layer is the gate Provided between the electrode and the semiconductor layer.

  In the present invention, the fluorine compound-containing layer may be provided at any position between the gate insulating layer and the semiconductor layer, in the gate insulating layer, between the gate electrode and the gate insulating layer. More preferably, the gate insulating layer is provided so as to be in contact with the semiconductor layer between the gate insulating layer and the semiconductor layer. Two or more fluorine compound-containing layers may be provided at a plurality of positions, or a plurality of layers made of different materials may be laminated.

(Gate insulation layer)
Although various insulating films can be used as the gate insulating layer of the thin film transistor of the present invention, an inorganic oxide film having a high relative dielectric constant is particularly preferable. Inorganic oxides include silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium strontium titanate, barium zirconate titanate, lead zirconate titanate, lead lanthanum titanate, strontium titanate, Examples thereof include barium titanate, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate niobate, and yttrium trioxide. Of these, silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide are preferable. Inorganic nitrides such as silicon nitride and aluminum nitride can also be suitably used.

  Examples of the method for forming the film include a vacuum process, a molecular beam epitaxial growth method, an ion cluster beam method, a low energy ion beam method, an ion plating method, a CVD method, a sputtering method, an atmospheric pressure plasma method, and a spray process. Wet processes (solution processes) such as coating methods, spin coating methods, blade coating methods, dip coating methods, casting methods, roll coating methods, bar coating methods, die coating methods, etc., and methods such as printing and inkjet patterning. Can be used depending on the material.

  Among these, the atmospheric pressure plasma method or the wet process (solution process) is preferable.

  The wet process (solution process) is a method of applying and drying a liquid in which fine particles of inorganic oxide are dispersed in an arbitrary organic solvent or water using a dispersion aid such as a surfactant as required. A sol-gel method of applying and drying a solution of a precursor, for example, an alkoxide body can be used, but a thin film of an inorganic polymer material such as polysilazane containing a Si—N bond is formed by coating, and this is heated. Those converted into an inorganic film containing silicon oxide or titanium oxide as a main component by oxidation treatment are preferable.

  These inorganic polymer materials, for example, polysilazane (perhydropolysilazane) are commercially available as AZ Electronic Materials Co., Ltd., Aquamica NP110, NN110, and the like.

The conversion from an inorganic polymer material to an inorganic film is generally performed by heat treatment, but can also be performed by UV ozone oxidation, O ₂ plasma oxidation, etc., and a combination with thermal oxidation is also effective. The heat treatment is preferably performed in the presence of water vapor or oxygen because the conversion reaction proceeds quickly.

  It is also preferable that the gate insulating layer (film) is composed of an anodized film or the anodized film and an insulating film. The anodized film is preferably sealed. The anodized film is formed by anodizing a metal that can be anodized by a known method.

  Examples of the metal that can be anodized include aluminum and tantalum, and the anodizing method is not particularly limited, and a known method can be used.

  Examples of organic compound films include polyimides, polyamides, polyesters, polyacrylates, photo-radical polymerization-type, photo-cation polymerization-type photo-curing resins, copolymers containing acrylonitrile components, polyvinyl phenol, polyvinyl alcohol, novolac resins, etc. Can also be used.

  Examples of the method for forming the organic compound film include spray coating, spin coating, blade coating, dip coating, dip coating, casting, roll coating, bar coating, and die coating. A wet process (solution process) such as a patterning method can be used.

  An inorganic oxide film and an organic compound film can be laminated and used together. The thickness of these insulating films is generally 50 nm to 3 μm, preferably 100 nm to 1 μm.

(Oxide semiconductor)
In the present invention, the oxide semiconductor is a metal oxide. In the present invention, a thin film of a material containing a metal component of a metal oxide semiconductor and serving as a precursor of the metal oxide semiconductor is provided, and then the thin film is thermally oxidized. A semiconductor thin film is obtained by performing a semiconductor conversion process such as the above to convert it into a metal oxide semiconductor.

  Examples of the metal oxide semiconductor precursor include a metal atom-containing compound, and examples of the metal atom-containing compound include metal salts, metal halide compounds, and organic metal compounds containing a metal atom.

  Metals of metal salts, halogen metal compounds, and organometallic compounds include Li, Be, B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu Zn, Ga, Ge, Rb, Sr, Y, Zr, Nb, Mo, Cd, In, Ir, Sn, Sb, Cs, Ba, La, Hf, Ta, W, Tl, Pb, Bi, Ce, Pr Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and the like.

  In the present invention, these metal salts preferably contain one or more of any of indium (In), tin (Sn), and zinc (Zn), and may be used in combination.

  Moreover, it is preferable that the other metal contains a salt of either gallium (Ga) or aluminum (Al).

  As metal salts, nitrates, acetates and the like can be suitably used, and as halogen metal compounds, chlorides, iodides, bromides and the like can be suitably used.

  Examples of the organometallic compound include those represented by the following general formula (I).

Formula (I) R ¹ _x MR ² _y R ³ _z
In the formula, M is a metal, R ¹ is an alkyl group, R ² is an alkoxy group, R ³ is a β-diketone complex group, a β-ketocarboxylic acid ester complex group, a β-ketocarboxylic acid complex group, and a ketooxy group (ketooxy complex group). X + y + z = m, x = 0 to m, or x = 0 to m−1, and y = 0 to m, z = 0. ~ M, each of which is 0 or a positive integer. Examples of the alkyl group for R ¹ include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkoxy group for R ² include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and a 3,3,3-trifluoropropoxy group. Further, a hydrogen atom in the alkyl group may be substituted with a fluorine atom. Examples of the group selected from the β-diketone complex group, the β-ketocarboxylic acid ester complex group, the β-ketocarboxylic acid complex group, and the ketooxy group (ketooxy complex group) of R ³ include, for example, 2,4 -Pentanedione (also called acetylacetone or acetoacetone), 1,1,1,5,5,5-hexamethyl-2,4-pentanedione, 2,2,6,6-tetramethyl-3,5-heptanedione , 1,1,1-trifluoro-2,4-pentanedione and the like, as the β-ketocarboxylic acid ester complex group, for example, acetoacetic acid methyl ester, acetoacetic acid ethyl ester, acetoacetic acid propyl ester, trimethylacetate Examples thereof include ethyl acetate, methyl trifluoroacetoacetate and the like. As β-ketocarboxylic acid, For example, acetoacetic acid, trimethylacetoacetic acid and the like can be mentioned, and examples of ketooxy include acetooxy group (or acetoxy group), propionyloxy group, butyryloxy group, acryloyloxy group, methacryloyloxy group and the like. These groups preferably have 18 or less carbon atoms. Further, it may be linear or branched, or a hydrogen atom may be a fluorine atom. Among organometallic compounds, those having at least one oxygen in the molecule are preferable. As such, an organometallic compound containing at least one alkoxy group of R ² , a β-diketone complex group, a β-ketocarboxylic acid ester complex group, a β-ketocarboxylic acid complex group and a ketooxy group (ketooxy group) of R ³ Most preferred are metal compounds having at least one group selected from (complex groups). Among the metal salts, nitrate is preferable. Nitrate is easily available as a high-purity product and has high solubility in water, which is preferable as a medium for use. Examples of nitrates include indium nitrate, tin nitrate, zinc nitrate, and gallium nitrate.

  Of the above metal oxide semiconductor precursors, metal nitrates, metal halides, and alkoxides are preferable. Specific examples include indium nitrate, zinc nitrate, gallium nitrate, tin nitrate, aluminum nitrate, indium chloride, zinc chloride, tin chloride (divalent), tin chloride (tetravalent), gallium chloride, aluminum chloride, tri-i-. Examples include propoxyindium, diethoxyzinc, bis (dipivaloylmethanato) zinc, tetraethoxytin, tetra-i-propoxytin, tri-i-propoxygallium, and tri-i-propoxyaluminum.

  In particular, in the present invention, it is preferable to use a metal salt selected from nitrate, sulfate, phosphate, carbonate, acetate or oxalate as a precursor of the metal oxide semiconductor.

  In the present invention, a TFT element having a high carrier mobility by using a metal salt selected from nitrate, sulfate, phosphate, carbonate, acetate or oxalate of the above metal as a precursor is used. A metal oxide semiconductor having good characteristics with a large off ratio can be obtained.

  These metal salts have less energy of oxidation reaction, which is expected to include hydrolysis and dehydration reactions, compared to the case of using other inorganic salts and organic metal compounds, and there are decomposition products generated during the oxide formation process. It is presumed that good semiconductor characteristics can be obtained because it is difficult to remain in the film because it is efficiently vaporized and discharged, and there are few impurity components such as carbon present in the generated oxide.

  Among the above metal salts, nitrates are most preferable from the viewpoint of reducing impurities and improving semiconductor characteristics.

  The effect of improving the semiconductor properties obtained with metal salts, particularly nitrates, is particularly remarkable in an amorphous metal oxide semiconductor obtained at a temperature range of 100 ° C. or higher and 400 ° C. or lower. It has not been known so far that a good state of an amorphous oxide semiconductor can be obtained with a semiconductor thin film made of a metal salt as a raw material, which can be said to be a remarkable effect obtained by the present invention.

  Use of these salts is also preferable because the irradiation time can be shortened when the semiconductor conversion treatment is performed at substantially low temperatures by electromagnetic waves (microwaves).

(Precursor thin film formation method, patterning method)
In order to form a thin film containing these metal oxide semiconductor precursors, a known film formation method, vacuum deposition method, molecular beam epitaxial growth method, ion cluster beam method, low energy ion beam method, ion plating method are used. In the present invention, a solution prepared by dissolving the above-mentioned metal oxide semiconductor precursor in an appropriate solvent is applied on the substrate. Is preferable, and thus productivity can be greatly improved.

  The solvent for dissolving the precursor of the metal oxide semiconductor is not particularly limited as long as it dissolves the metal compound to be used in addition to water, and water and alcohols such as ethanol, propanol, and ethylene glycol, Ethers such as tetrahydrofuran and dioxane, esters such as methyl acetate and ethyl acetate, ketones such as acetone, methyl ethyl ketone and cyclohexanone, glycol ethers such as diethylene glycol monomethyl ether, acetonitrile, and aromatics such as xylene and toluene Solvents such as α-terpineol such as hexane, cyclohexane and tridecane, alkyl halide solvents such as chloroform and 1,2-dichloroethane, N-methylpyrrolidone, carbon disulfide and the like can be used.

  Among these, water and lower alcohols are preferable from the viewpoint of solubility of metal salts and the like and drying properties after coating, and methanol, ethanol, and propanol (1-propanol and isopropanol) are preferable among the lower alcohols from the viewpoint of drying properties. Moreover, a lower alcohol may be used alone as a solvent, or may be used by mixing with water at an arbitrary ratio. From the viewpoints of solubility, solution stability, and drying properties, it is preferable to prepare “aqueous solution” of the present invention by mixing water and these lower alcohols. It is preferable to prepare an aqueous solution by mixing a lower alcohol, since the surface tension can be lowered without causing a large change in composition, and the light emission is improved in inkjet coating or the like.

  The aqueous solution of the present invention is a mixed solvent having a water content of 30% by mass or more in the solvent and water (water content = 100% by mass) as a solute (in the present invention, a metal salt and other additives added as necessary. ) Is dissolved. From the viewpoints of solubility of solutes such as metal salts and solution stability, the water content is preferably 50% by mass or more, and more preferably 70% by mass or more.

  In addition, when considering semiconductor characteristics such as drying characteristics, inkjet emission characteristics, and thin film transistor characteristics, it is preferable to add a lower alcohol with a solvent ratio of 5% by mass or more, and satisfy any characteristics (drying, emission characteristics and solution stability). The water / lower alcohol ratio is preferably 5/5 to 95/5.

  Further, as an effect of adding alcohols, an effect of improving semiconductor characteristics is recognized. For example, improvement in characteristics such as mobility, on / off ratio, and threshold value of the thin film transistor is recognized. Although the cause of this effect is not clear, it is presumed that it has an influence on the oxide formation process by heating.

  In particular, a metal salt such as nitrate is not hydrolyzed at room temperature unlike metal alkoxides, and water can be used as a main solvent, so that it is more preferable in terms of manufacturing process and environment.

  In addition, metal salts such as metal chlorides are severely degraded and decomposed in the atmosphere (especially in the case of gallium and the like) and strong deliquescence, but inorganic salts such as nitrates are easy to use without deliquescence and deterioration This is also preferable in terms of the manufacturing environment.

  Among the metal salts, nitrates having the most excellent properties in performance such as degradation, decomposition, and easy dissolution in water and deliquescence are most preferable.

  In the present invention, a solution containing a metal salt or the like is applied onto a substrate to form a thin film containing a metal oxide semiconductor precursor.

  As a method of forming a metal oxide semiconductor precursor thin film by applying a solution containing a metal salt or the like on a substrate, a spray coating method, a spin coating method, a blade coating method, a dip coating method, a casting method, Examples include roll coating methods, bar coating methods, die coating methods, mist methods, printing methods such as relief printing, intaglio printing, lithographic printing, screen printing, and ink jet printing, and methods using coating in a broad sense. The method etc. are mentioned. The coating film may be patterned by photolithography, laser ablation, or the like. Among these, the ink jet method, spray coating method, etc. which can apply | coat a thin film are preferable.

  For example, when forming a film using an inkjet method, a semiconductor precursor layer thin film containing a metal salt is formed by dropping a metal salt solution and volatilizing a solvent (water) at about 80 ° C. to 100 ° C. In addition, when dropping the solution, it is preferable that the substrate itself is heated to about 80 ° C. to 150 ° C. because two processes of coating and drying can be performed simultaneously and the film forming property of the precursor film is good.

(Composition ratio of metal)
By the method of the present invention, a metal oxide semiconductor thin film containing a single metal atom or a plurality of metal atoms selected from the metal atoms described above is produced. As the metal oxide semiconductor, any state of single crystal, polycrystal, and amorphous can be used, but an amorphous thin film is preferably used.

  The metal atom contained in the formed metal oxide semiconductor preferably contains any one of indium (In), tin (Sn), and zinc (Zn), as described in the description of the precursor. It is preferable to contain gallium (Ga) or aluminum (Al).

  When preparing a precursor solution containing these metals as components, the preferred metal composition ratio is as follows: a metal (metal A) contained in a salt selected from metal salts of In and Sn, and metal salts of Ga and Al The molar ratio (metal A: metal B: metal C) of metal (metal B = metal C) contained in the metal salt (metal B) contained in the salt selected from the following relational expression: It is preferable to satisfy.

Metal A: Metal B: Metal C = 1: 0.2-1.5: 0-5
It is.

  As the metal salt, nitrate is most preferable. Therefore, the molar ratio (A: B: C) of In, Sn (metal A), Ga, Al (metal B), and Zn (metal C) is as described above. It is preferable to form a precursor thin film containing a metal inorganic salt by coating using a coating solution in which nitrate of each metal is dissolved and formed in a solvent containing water as a main component so as to satisfy the formula.

  Moreover, the film thickness of the thin film containing the metal inorganic salt used as a precursor is 1-200 nm, More preferably, it is 5-100 nm.

(Amorphous oxide)
As the metal oxide semiconductor to be formed, any state of single crystal, polycrystal, and amorphous can be used, but an amorphous thin film is preferably used. Being amorphous can be confirmed by X-ray diffraction or electron diffraction, and can be regarded as amorphous if a diffraction pattern unique to the crystal is not observed.

The electron carrier concentration of an amorphous oxide, which is a metal oxide according to the present invention, formed from a metal compound material that is a precursor of a metal oxide semiconductor only needs to be less than 10 ¹⁸ / cm ³ . The electron carrier concentration is a value when measured at room temperature. The room temperature is, for example, 25 ° C., specifically, a certain temperature appropriately selected from the range of about 0 ° C. to 40 ° C. Note that the electron carrier concentration of the amorphous oxide according to the present invention does not need to satisfy less than 10 ¹⁸ / cm ³ in the entire range of 0 ° C. to 40 ° C. For example, a carrier electron density of less than 10 ¹⁸ / cm ³ may be realized at 25 ° C. Further, when the electron carrier concentration is further reduced to 10 ¹⁷ / cm ³ or less, more preferably 10 ¹⁶ / cm ³ or less, a normally-off TFT can be obtained with a high yield.

  The electron carrier concentration can be measured by Hall effect measurement.

  The film thickness of the semiconductor that is a metal oxide is not particularly limited, but the characteristics of the obtained transistor are often greatly influenced by the film thickness of the semiconductor film, and the film thickness varies depending on the semiconductor. Generally, 1 μm or less, particularly 10 to 300 nm is preferable.

In the present invention, the precursor material (metal salt), composition ratio, production conditions, and the like are controlled so that, for example, the electron carrier concentration is 10 ¹² / cm ³ or more and less than 10 ¹⁸ / cm ³ . More preferably, it is in the range of 10 ¹³ / cm ³ or more and 10 ¹⁷ / cm ³ or less, and more preferably 10 ¹⁵ / cm ³ or more and 10 ¹⁶ / cm ³ or less.

  Examples of the semiconductor conversion treatment, that is, a method of converting a precursor thin film formed from a metal inorganic salt into a metal oxide semiconductor include oxidation treatments such as an oxygen plasma method, a thermal oxidation method, and a UV ozone method. Moreover, the microwave irradiation mentioned later can be used.

  In the present invention, the temperature at which the precursor material is heated can be arbitrarily set within the range of the temperature of the thin film surface containing the precursor in the range of 50 ° C to 1000 ° C. From a viewpoint, it is preferable to set it as 100 to 400 degreeC. The temperature of the thin film surface, the temperature of the substrate, etc. can be measured by a surface thermometer using a thermocouple, a radiation thermometer capable of measuring the radiation temperature, a fiber thermometer, or the like. Can be measured. The heating temperature can be controlled by the output of electromagnetic waves, the irradiation time, and the number of irradiations. The time for heating the precursor material can be set arbitrarily, but is preferably in the range of 1 second to 60 minutes from the viewpoint of the characteristics of the electronic device and production efficiency. More preferably, it is 5 minutes to 30 minutes.

  In the present invention, the semiconductor conversion treatment can be performed at a relatively low temperature by using a metal salt selected from nitrate, sulfate, phosphate, carbonate, acetate or oxalate.

  Further, the formation of the metal oxide can be detected by ESCA or the like, and the conditions under which the conversion to the semiconductor is sufficiently performed can be selected in advance.

  Further, it is preferable to use an atmospheric pressure plasma method as the oxygen plasma method. In the oxygen plasma method and the UV ozone method, the substrate is preferably heated in the range of 50 ° C to 300 ° C.

  In the atmospheric pressure plasma method, an inert gas such as argon gas is used as a discharge gas under atmospheric pressure, and a reaction gas (a gas containing oxygen) is introduced into the discharge space, and a high frequency electric field is applied to the discharge gas. Is excited to generate plasma, and contact with a reactive gas to generate plasma containing oxygen, and the substrate surface is exposed to this to perform oxygen plasma treatment. Under atmospheric pressure represents a pressure of 20 to 110 kPa, preferably 93 to 104 kPa.

  Using an atmospheric pressure plasma method, oxygen plasma is generated as a reactive gas, oxygen plasma is generated, and the precursor thin film containing a metal salt is exposed to the plasma space, so that the precursor thin film is oxidized and decomposed by plasma oxidation. A layer made of a metal oxide is formed.

The high frequency power source is 0.5 kHz or more and 2.45 GHz or less, and the power supplied between the counter electrodes is preferably 0.1 W / cm ² or more and 50 W / cm ² or less.

  The gas used is basically a mixed gas of a discharge gas (inert gas) and a reaction gas (oxidizing gas). The reaction gas is preferably oxygen gas and is preferably contained in an amount of 0.01 to 10% by volume with respect to the mixed gas. Although it is more preferable that it is 0.1-10 volume%, More preferably, it is 0.1-5 volume%.

  Examples of the inert gas include Group 18 elements of the periodic table, specifically, helium, neon, argon, krypton, xenon, radon, nitrogen gas, and the like, in order to obtain the effects described in the present invention. For this, helium, argon, or nitrogen gas is preferably used.

  In order to introduce the reaction gas between the electrodes which are the discharge space, normal temperature and normal pressure may be used.

  The plasma method under atmospheric pressure is described in JP-A Nos. 11-61406, 11-133205, 2000-121804, 2000-147209, 2000-185362, and the like.

  The UV ozone method is a method in which an ultraviolet light is irradiated in the presence of oxygen to advance an oxidation reaction. It is preferable to irradiate so-called vacuum ultraviolet light having a wavelength of ultraviolet light of 100 nm to 450 nm, particularly preferably about 150 to 300 nm. As the light source, a low-pressure mercury lamp, a deuterium lamp, a xenon excimer lamp, a metal halide lamp, an excimer laser, or the like can be used.

The output of the lamp ^{400W~30kW, 100mW / cm 2 ~100kW /} cm 2 as illuminance, preferably 10~5000mJ / cm ² as irradiation energy, 100 to 2000 mJ / cm ² is more preferable.

The illuminance at the time of ultraviolet irradiation is preferably 1 mW to 10 W / cm ² .

  In the present invention, it is preferable to perform a heat treatment after the oxidation treatment or simultaneously with the oxidation treatment in addition to the oxidation treatment. Thereby, oxidative decomposition can be promoted.

  Moreover, after oxidizing the thin film containing a metal salt, the substrate may be heated in the range of 50 ° C. to 200 ° C., preferably in the range of 80 ° C. to 150 ° C., and the heating time in the range of 1 minute to 10 hours. preferable.

  The heat treatment may be performed at the same time as the oxidation treatment, and can be quickly converted into a metal oxide semiconductor by oxidation.

  After the conversion to a metal oxide semiconductor, the thickness of the formed semiconductor thin film is preferably 1 to 200 nm, more preferably 5 to 100 nm.

  In the present invention, the semiconductor conversion process preferably includes a microwave (0.3 to 50 GHz) irradiation step. In addition, it is preferable to irradiate microwaves in the presence of oxygen in order to advance the oxidation reaction of the metal oxide semiconductor precursor in a short time.

(Microwave irradiation)
In the present invention, it is preferable to use microwave irradiation as a method of converting a thin film formed from the metal inorganic salt material, which is a precursor of a metal oxide semiconductor, into a semiconductor.

  That is, after forming a thin film containing the metal salt material to be a precursor of these metal oxide semiconductors, the thin film is irradiated with electromagnetic waves, particularly microwaves (frequency 0.3 GHz to 50 GHz).

  By irradiating the thin film containing the metal salt material, which is the precursor of the metal oxide semiconductor, with microwaves, the electrons in the metal oxide precursor vibrate and heat is generated to uniformly heat the thin film from the inside. Is done. Since substrates such as glass and resin have almost no absorption in the microwave region, the substrate itself hardly generates heat, and only the thin film portion can be selectively heated to be thermally oxidized and converted into a metal oxide semiconductor. Become.

  As is generally the case with microwave heating, microwave absorption concentrates on strongly absorbing substances and can be raised in a very short time, so when this method is used in the present invention, The base material itself is hardly affected by heating by electromagnetic waves, and only the precursor thin film can be heated to a temperature at which the oxidation reaction occurs in a short time, and the metal oxide precursor can be converted into a metal oxide. . Further, the heating temperature and the heating time can be controlled by the output of the microwave to be irradiated and the irradiation time, and can be adjusted according to the precursor material and the substrate material.

  Generally, a microwave refers to an electromagnetic wave having a frequency of 0.3 GHz to 50 GHz, and is used in 0.8 GHz and 1.5 GHz bands, 2 GHz bands, amateur radio, aircraft radar, etc. used in mobile communication. .2 GHz band, microwave oven, local radio, 2.4 GHz band used for VICS, 3 GHz band used for ship radar, etc., and 5.6 GHz used for other ETC communications are all electromagnetic waves in the microwave category. is there. In addition, oscillators such as 28 GHz and 50 GHz are available on the market.

  Compared with a normal heating method using an oven or the like, a better metal oxide semiconductor layer can be obtained by using the heating method by electromagnetic wave (microwave) irradiation of the present invention. In producing a metal oxide semiconductor from a metal oxide semiconductor precursor material, effects other than conduction heat, for example, an effect suggesting direct action of electromagnetic waves on the metal oxide semiconductor precursor material are obtained. Although the mechanism has not been fully clarified, it is presumed that the conversion of the metal oxide semiconductor precursor material into a metal oxide semiconductor by hydrolysis, dehydration, decomposition, oxidation, or the like was promoted by electromagnetic waves.

  The method of performing semiconductor conversion treatment by irradiating the semiconductor precursor layer containing the metal salt with microwaves is a method of allowing the oxidation reaction to proceed selectively in a short time. Note that irradiation with microwaves in the presence of oxygen is preferable in order to advance the oxidation reaction of the metal oxide semiconductor precursor in a short time. However, since heat is transferred to the base material not only by heat conduction, in the case of a base material with low heat resistance such as a resin substrate, the precursor can be controlled by controlling the microwave output, irradiation time, and the number of times of irradiation. It is preferable to process so that the surface temperature of the thin film containing a body may be 100 degreeC or more and less than 400 degreeC. The temperature of the thin film surface, the temperature of the substrate, etc. can be measured by a surface thermometer using a thermocouple or a non-contact surface thermometer.

  Further, when a strong electromagnetic wave absorber such as ITO is present in the vicinity (for example, a gate electrode), this also absorbs microwaves and generates heat, so that a region adjacent thereto can be heated in a shorter time.

(Element structure)
FIG. 1 is a diagram showing a typical element configuration of a thin film transistor element using a metal oxide semiconductor according to the present invention.

  Several structural examples of thin film transistors are shown in cross-sectional views in FIGS. In FIG. 1, a source electrode 102 and a drain electrode 103 are connected to a semiconductor layer 101 made of a metal oxide semiconductor as a channel.

  In FIG. 6A, a source electrode 102 and a drain electrode 103 are formed on a support 106 by the method of the present invention, and this is used as a base material (substrate) to form a semiconductor layer 101 between both electrodes. A field effect thin film transistor is formed by forming a gate insulating layer 105 thereon and further forming a gate electrode 104 thereon. FIG. 4B shows the semiconductor layer 101 formed between the electrodes in FIG. 5A so as to cover the entire surface of the electrode and the support using a coating method or the like. (C) shows a structure in which the semiconductor layer 101 is first formed on the support 106, the source electrode 102, the drain electrode 103, and the insulating layer 105 are formed, and then the gate electrode 104 is formed. In the present invention, the semiconductor layer and the fluorine compound-containing layer (the fluorine compound-containing layer is not shown) may be formed by the configuration and method of the present invention.

  In FIG. 4D, after the gate electrode 104 is formed on the support 106, the gate insulating layer 105 is formed, the source electrode 102 and the drain electrode 103 are formed thereon, and the semiconductor layer 101 is formed between the electrodes. Form. In addition, the configuration as shown in FIGS.

  FIG. 2 is a schematic equivalent circuit diagram showing an example of a thin film transistor sheet in which a plurality of thin film transistor elements are arranged.

  The thin film transistor sheet 120 has a large number of thin film transistor elements 124 arranged in a matrix. 121 is a gate bus line of the gate electrode of each thin film transistor element 124, and 122 is a source bus line of the source electrode of each thin film transistor element 124. An output element 126 is connected to the drain electrode of each thin film transistor element 124. The output element 126 is, for example, a liquid crystal or an electrophoretic element, and constitutes a pixel in the display device. In the illustrated example, a liquid crystal is shown as an output element 126 by an equivalent circuit composed of a resistor and a capacitor. Reference numeral 125 denotes a storage capacitor, 127 denotes a vertical drive circuit, and 128 denotes a horizontal drive circuit. The present invention can be used to manufacture the source, drain electrode, gate electrode, and the like of each transistor element in the thin film transistor sheet 120, as well as the gate bus line, source bus line, and circuit wiring.

  Next, each element constituting the TFT element will be described.

(electrode)
In the present invention, the conductive material used for the electrodes such as the source electrode, the drain electrode, and the gate electrode constituting the TFT element is not particularly limited as long as it has conductivity at a practical level as an electrode. , Gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tin / antimony oxide, indium / tin oxide ( ITO), fluorine-doped zinc oxide, zinc, carbon, graphite, glassy carbon, silver paste and carbon paste, lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium, manganese, zirconium, gallium, niobium, sodium Sodium - potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, a magnesium / silver mixture, a magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide mixture, a lithium / aluminum mixture, or the like is used.

  Moreover, as a conductive material, a conductive polymer, metal fine particles, or the like can be suitably used. As the dispersion containing metal fine particles, for example, a known conductive paste may be used, but a dispersion containing metal fine particles having a particle diameter of 1 nm to 50 nm, preferably 1 nm to 10 nm is preferable. In order to form an electrode from metal fine particles, the above-described method can be used in the same manner, and the metal described above can be used as the material of the metal fine particles.

(Method for forming electrodes, etc.)
As a method for forming an electrode, a method for forming an electrode using a known photolithographic method or a lift-off method, using a conductive thin film formed by a method such as vapor deposition or sputtering using the above as a raw material, or a metal foil such as aluminum or copper There is a method in which a resist is formed and etched by thermal transfer, ink jet or the like. Alternatively, a conductive polymer solution or dispersion, a dispersion containing metal fine particles, or the like may be directly patterned by an ink jet method, or may be formed from a coating film by lithography or laser ablation. Further, a method of patterning a conductive ink or conductive paste containing a conductive polymer or metal fine particles by a printing method such as relief printing, intaglio printing, planographic printing, or screen printing can also be used.

  As a method of forming an electrode such as a source, drain, or gate electrode, a gate, or a source bus line without patterning a metal thin film using a photosensitive resin such as etching or lift-off, there is a method by an electroless plating method. Are known.

  Regarding the method of forming an electrode by electroless plating, as described in Japanese Patent Application Laid-Open No. 2004-158805, a liquid containing a plating catalyst that causes electroless plating by acting with a plating agent on a portion where an electrode is provided After patterning, for example, by a printing method (including inkjet printing), a plating agent is brought into contact with a portion where an electrode is provided. If it does so, electroless plating will be performed to the said part by the contact of the said catalyst and a plating agent, and an electrode pattern will be formed.

  The application of the electroless plating catalyst and the plating agent may be reversed, and the pattern formation may be performed either. However, a method of forming a plating catalyst pattern and applying the plating agent to this is preferable.

  As the printing method, for example, screen printing, planographic printing, letterpress printing, intaglio printing, printing by ink jet printing, or the like is used.

(substrate)
Various materials can be used as the support material constituting the substrate (support). For example, ceramic substrates such as glass, quartz, aluminum oxide, sapphire, silicon nitride, silicon carbide, silicon, germanium, gallium A semiconductor substrate such as arsenic, gallium phosphide, gallium nitrogen, paper, non-woven fabric or the like can be used. In the present invention, the support is preferably made of a resin, for example, a plastic film sheet can be used. Examples of plastic films include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), and cellulose. Examples include films made of triacetate (TAC), cellulose acetate propionate (CAP), and the like. By using a plastic film, the weight can be reduced as compared with the case of using a glass substrate, the portability can be improved, and the resistance to impact can be improved.

  An element protective layer can be provided on the thin film transistor element of the present invention. Examples of the protective layer include the inorganic oxides and inorganic nitrides described above, and it is preferable to form the protective layer by the atmospheric pressure plasma method described above.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. Unless otherwise specified, “part” or “%” in the examples represents “part by mass” or “mass%”.

Example 1
A thin film transistor element having a bottom gate / top contact configuration was fabricated.

  Hereinafter, the thin film transistor element having the configuration shown in FIGS. 3A, 3B, 3C, and 3D will be described as an example, but the present invention is not limited thereto.

A polyimide film (thickness: 200 μm) was used as the support 106 (FIG. 3A), and a corona discharge treatment was first performed on the polyimide film under the condition of 50 W / m ² / min. Thereafter, an undercoat layer was formed in order to improve adhesion as follows.

(Formation of undercoat layer)
A coating solution having the following composition was applied to a dry film thickness of 2 μm, dried at 90 ° C. for 5 minutes, and then cured for 4 seconds from a distance of 10 cm under a 60 W / cm high-pressure mercury lamp.

Dipentaerythritol hexaacrylate monomer 60g
Dipentaerythritol hexaacrylate dimer 20g
Dipentaerythritol hexaacrylate trimer or higher component 20g
Diethoxybenzophenone UV initiator 2g
Silicone surfactant 1g
75g of methyl ethyl ketone
Methyl propylene glycol 75g
Further, a silicon oxide film having a thickness of 50 nm was provided on the layer by continuous atmospheric pressure plasma treatment under the following conditions, and these layers were used as undercoat layers (not shown in the figure).

(Used gas)
Inert gas: helium 98.25% by volume
Reactive gas: oxygen gas 1.5 volume%
Reactive gas: Tetraethoxysilane vapor (bubbled with helium gas) 0.25% by volume
(Discharge conditions)
High frequency power supply: 13.56 MHz
Discharge output: 10 W / cm ²
(Electrode condition)
The electrode is coated with 1 mm of alumina by ceramic spraying on a stainless steel jacket roll base material having cooling means with cooling water, and then a solution obtained by diluting tetramethoxysilane with ethyl acetate is applied and dried, and then sealed by ultraviolet irradiation. This is a roll electrode having a dielectric (relative permittivity of 10) that has been subjected to hole treatment and has a smooth surface and an Rmax of 5 μm, and is grounded. On the other hand, as the application electrode, a hollow rectangular stainless steel pipe was coated with the same dielectric as described above under the same conditions.

  Next, a gate electrode is formed. An ITO film having a thickness of 150 nm was formed on one surface by sputtering, and then etched by photolithography to form a gate electrode 104 (FIG. 3A).

(Formation process of gate insulating layer and fluorine compound-containing layer)
(Preparation of thin film transistor 1)
Aquamica NP110-10 (perhydropolysilazane / amine-based catalyst / xylene 10 mass% solution: manufactured by AZ Electronic Materials Co., Ltd.) is spin-coated (2000 rpm × 30 sec) on the support on which the gate electrode 104 produced above is formed. ) And dried to form an insulating film precursor layer. Next, heat treatment is performed on the hot plate (200 ° C.) for 1 hour in the atmosphere to form a gate insulating layer (film) 105 (FIG. 3A) (film thickness 180 nm) which is a SiO ₂ film converted from polysilazane. Formed.

Subsequently, after the substrate on which the gate insulating layer (film) 105 was formed was immersed in a toluene solution (0.1 mass%, room temperature) in which CF ₃ (CH ₂ ) ₉ Si (OEt) ₃ was dissolved, By rinsing with toluene and drying, a fluorine compound-containing layer 107 (FIG. 3A) in which CF ₃ (CH ₂ ) ₉ Si groups were self-organized and aligned was formed on the surface of the gate insulating film.

  Next, a semiconductor layer is formed.

(Formation of semiconductor precursor thin film and semiconductor layer (IGZO) (precursor coating method))
10 masses of indium nitrate [In (NO ₃ ) ₃ ], zinc nitrate [Zn (NO ₃ ) ₂ ], and gallium nitrate [Ga (NO ₃ ) ₃ ] mixed at a metal ratio of 1: 1: 1 (molar ratio). The ink was applied to the channel forming portion while keeping the substrate temperature at 100 ° C. using an aqueous solution prepared as a% aqueous solution, treated at 150 ° C. for 10 minutes and dried to form a semiconductor precursor thin film.

  Then, using this substrate with a multimode type 2.45 GHz microwave irradiator (μ-reactor manufactured by Shikoku Keiki Kogyo Co., Ltd.), the microwave (2 .45 GHz). Only the semiconductor surface side is kept warm with a heat insulating material, and after heating up to 300 ° C. at 500 W output using a thermocouple surface thermometer, the surface temperature of the thin film is kept at 300 ° C. while PID controlling the microwave output. Microwave irradiation was performed for 30 minutes. The semiconductor precursor material thin film was converted into the semiconductor layer 101 (FIG. 3A).

  Next, gold was deposited through a mask to form a source electrode 102 and a drain electrode 103, and a thin film transistor element was manufactured. Each size was 10 μm wide, 50 μm long (channel width) and 50 nm thick, and the distance between the source electrode and the drain electrode (channel length) was 15 μm.

  Thus, a thin film transistor 1 (the present invention) was produced (FIG. 3A).

(Production of thin film transistor 2 (comparative))
In producing the thin film transistor 1, except that the fluorine compound-containing layer was not formed,
Similarly, a thin film transistor 2 (comparative) was produced.

(Production of thin film transistor 3 (comparative))
In the production of the thin film transistor 1, the production of the semiconductor layer 101 (formation of a semiconductor precursor thin film and a semiconductor layer (precursor coating method)) was replaced with the production of the semiconductor layer 1 (sputtering method) as follows. Similarly, a thin film transistor 3 (comparative) was produced.

(Semiconductor layer formation (sputtering method))
A semiconductor layer was formed by sputtering. As a sputtering target, a composite oxide with an In: Ga: Zn composition ratio of 1: 1: 1 was used, and a film was formed by a DC magnetron type sputtering apparatus. (If necessary, patterning can be performed using a normal photolithographic etching method, and a commercially available product for ITO can be used as the etchant). The average thickness of the formed oxide semiconductor layer 101 was 30 nm (FIG. 3A).

(Production of thin film transistor 4 (comparative))
In the production of the thin film transistor 3, except that the fluorine compound-containing layer was not formed,
Similarly, a thin film transistor 4 (comparative) was produced.

(Production of Thin Film Transistor 5 (Invention))
In the fabrication of the thin film transistor 1, the formation of the fluorine compound-containing layer in which CF ₃ (CH ₂ ) ₉ Si groups are self-organized and aligned is replaced with the formation of a fluorine compound-containing layer made of Cytop as follows. A thin film transistor 5 (the present invention) was produced in the same manner as others.

(Formation of a fluorine compound-containing layer consisting of CYTOP)
On a gate insulating layer (film), CTL-809M (Cytop, Asahi Glass fluorine resin, 9% by mass perfluorotributylamine solution) was diluted to 5% by mass, and spin coating (4000 rpm × 30 seconds), and then dried and heated at 180 ° C. for 1 hour to form a fluorine compound-containing layer (thickness: 160 nm) made of CYTOP on the gate insulating film.

(Production of Thin Film Transistor 6 (Invention))
In the manufacture of the thin film transistor 5 (the present invention), the thin film transistor 6 was similarly formed except that a gate insulating film made of a polyvinylphenol film was provided as a gate insulating layer instead of the SiO ₂ film converted from polysilazane as follows. (Invention) was prepared.

(Formation of gate insulating film made of polyvinylphenol)
On a support having a gate electrode, poly 4-vinylphenol, poly (melamine-co-formaldehyde) methylate 84 mass% 1-butanol solution, propylene glycol monomethyl ether acetate is in a mass ratio of 10: 5: 85. Using the solution thus mixed, spin coating (6000 rpm × 30 sec) was applied, followed by drying and heating at 200 ° C. for 2 hours to form a gate insulating film (film thickness 300 nm) made of polyvinylphenol. .

(Production of thin film transistor 7 (comparative))
Thin film transistor 6 (Invention) A thin film transistor 7 (comparative) was prepared in the same manner except that the fluorine compound-containing layer made of Cytop was not provided.

(Production of Thin Film Transistor 8 (Invention))
In manufacturing the thin film transistor 6 (the present invention), instead of the semiconductor layer IGZO (In, Ga, Zn oxide) (precursor coating method), the semiconductor layer IGO (In, Ga oxide) (precursor coating method) is performed as follows. The thin film transistor 8 (the present invention) was produced in the same manner except that the above was provided.

(Formation of semiconductor precursor thin film and semiconductor layer (IGO) (precursor coating method))
The substrate temperature was obtained by using a 10% by mass aqueous solution in which indium nitrate [In (NO ₃ ) ₃ ] and gallium nitrate [Ga (NO ₃ ) ₃ ] were mixed at a metal ratio of 1: 0.5 (molar ratio). Was kept at 100 ° C. by ink-jet coating on the channel forming portion, treated at 150 ° C. for 10 minutes and dried to form a semiconductor precursor thin film.

  Then, using this substrate with a multimode type 2.45 GHz microwave irradiator (μ-reactor manufactured by Shikoku Keiki Kogyo Co., Ltd.), the microwave (2 .45 GHz). Only the semiconductor surface side is kept warm with a heat insulating material, and after heating up to 300 ° C. at 500 W output using a thermocouple surface thermometer, the surface temperature of the thin film is kept at 300 ° C. while PID controlling the microwave output. Microwave irradiation was performed for 30 minutes. The semiconductor precursor material thin film was converted into the semiconductor layer 101 (FIG. 3A).

(Preparation of thin film transistor 9 (present invention))
In the production of the thin film transistor 6 (invention), instead of providing the gate insulating layer and then the fluorine compound-containing layer, the order was reversed, except that the fluorine compound-containing layer and then the gate insulating layer were provided. Then, a thin film transistor 9 (the present invention) was produced (FIG. 3B).

(Production of Thin Film Transistor 10 (Invention))
In manufacturing the thin film transistor 6 (the present invention), instead of providing a gate insulating layer and then a fluorine compound-containing layer, a gate insulating layer and then a fluorine compound-containing layer are provided, and then a gate insulating layer (the gate A thin film transistor 10 (the present invention) was manufactured in the same manner except that the same as the insulating layer was provided (FIG. 3C).

(Production of Thin Film Transistor 11 (Invention))
In the production of the thin film transistor 6 (the present invention), instead of providing the gate insulating layer and then the fluorine compound-containing layer, the materials of the gate insulating layer and the fluorine compound-containing layer were mixed and used as described below. A thin film transistor 11 (the present invention) was produced in the same manner except that a layer (gate insulating layer = fluorine compound-containing layer) was provided.

(Preparation of polyvinylphenol and cytop mixed layer (gate insulation layer = fluorine compound-containing layer))
CYTOP solution, which is a solution obtained by diluting CTL-809M (CYTOP, Fluorine-based resin manufactured by Asahi Glass, 9 mass% perfluorotributylamine solution) with perfluorotributylamine to 5 mass%, and poly-4-vinyl A polyvinylphenol solution which is a liquid in which phenol, poly (melamine-co-formaldehyde) methylate 84 mass% 1-butanol solution, and propylene glycol monomethyl ether acetate are mixed at a mass ratio of 10: 5: 85. After mixing at 1: 1, and similarly applying by spin coating (4000 rpm × 30 sec), drying and heating at 200 ° C. for 2 hours, a polyvinylphenol / cytop mixed use layer (gate insulating layer = fluorine) Compound-containing layer) (film thickness 450 nm) was formed.

<Evaluation>
(Thin film transistor element characteristics (carrier mobility, on / off ratio))
The characteristics of each thin film transistor element were observed with respect to an increase in drain current (transfer characteristics) when the drain bias was 40 V and the gate bias was swept from −40 V to +40 V, and the mobility estimated from the saturation region ( The carrier mobility) (cm ² / Vs) and the on / off ratio (the ratio between the maximum current value and the minimum current value) were estimated. Ten elements were randomly selected for each level, and an average value of 10 elements was determined for each level, and determined as carrier mobility and on / off ratio.

(Rising voltage (V _on ))
The rising voltage (V _on ) is the value of the gate applied voltage (the point at which the drain current starts to increase (rises) when the gate bias is swept from −40 V to +40 V, that is, the point at which the off current is changed to the on current ( V). In the 10 elements selected for each level in the above-described evaluation of the thin film transistor element characteristics, the maximum value of the rising voltage V _on was V _{on / MAX} and the minimum value was V _{on / MIN} .

(S value)
The S value representing the sharpness of the rise from the off current to the on current was determined as follows. The drain current value at the rising voltage _{V on} is, when the applied gate voltage is _{V a} at a point became 1 × 10 ³ times, the difference between _{V a} and _{V on,} i.e., S value (V) = _{V a} - _Calculated as Von. The average value of 10 elements selected for each level in the evaluation of the thin film transistor element characteristics described above was obtained and used as the final S value.

(Performance variation between elements)
Performance variations between devices, when in a 10 element selected at each level in the evaluation of a thin film transistor device characteristics mentioned above, the maximum value of the threshold voltage _{V on V on / MAX,} the minimum value was _{V on / MIN,} V difference between _{on / MAX} and V _{on / MIN} , ie, V _{on / MAX} −V _{on / MIN}
Was evaluated as a performance variation between elements in accordance with the following evaluation criteria.
A: ( _{Von / MAX-} Von _{/ MIN} ) is less than 1V ○: ( _{Von / MAX-} Von _{/ MIN} ) is 1V or more and less than 5V Δ: ( _{Von / MAX-} Von _{/ MIN} ) is 5V or more and less than 15V ×: ( _{Von / MAX−} Von _{/ MIN} ) is 15V or more The results are shown in Table 2.

  From Table 2, in the case of the present invention, the mobility and the on / off ratio are excellent, and further, the shift to the negative side of the rising voltage, the S value deterioration, and the performance variation between elements are excellent. It can be seen that the thin film transistor is highly stable.

  According to the present invention, it can be formed by a simple process at a low temperature, has excellent mobility and on / off ratio, and further improves the negative voltage shift of rising voltage, S value deterioration, and performance variation between elements. It can be seen that a highly stable thin film transistor and a method for manufacturing the thin film transistor can be provided.

101 Semiconductor layer 102 Source electrode 103 Drain electrode 104 Gate electrode 105 Gate insulating layer 106 Support (substrate)
107 Fluorine compound-containing layer

Claims (11)

In a thin film transistor having a gate electrode, a gate insulating layer, a source electrode, a drain electrode, and a semiconductor layer on a substrate,
The semiconductor layer is made of an oxide semiconductor formed by coating,
A thin film transistor, wherein a fluorine compound-containing layer is provided between the gate electrode and the semiconductor layer.   2. The thin film transistor according to claim 1, wherein the fluorine compound-containing layer is provided between the gate insulating layer and the semiconductor layer.   The thin film transistor according to claim 1, wherein the fluorine compound-containing layer is provided in the gate insulating layer.   The thin film transistor according to claim 1, wherein the fluorine compound-containing layer is provided between the gate electrode and the gate insulating layer.   The thin film transistor according to any one of claims 1 to 4, wherein the fluorine compound-containing layer comprises a fluorine-based resin.   The thin film transistor according to claim 1, wherein the oxide semiconductor is made of an oxide semiconductor containing zinc or indium.   The oxide semiconductor is made of an oxide semiconductor containing an oxide containing zinc and indium, an oxide containing zinc and gallium, or an oxide containing indium and gallium. Thin film transistor.   The thin film transistor according to claim 6, wherein the oxide semiconductor is an oxide semiconductor containing an oxide made of zinc, indium, and gallium, or an oxide made of indium and gallium.   The thin film transistor according to claim 1, wherein the semiconductor layer is formed of a film formed by a solution process using a precursor of an oxide semiconductor.   The said semiconductor layer consists of a film | membrane formed by irradiating a microwave energy to the film | membrane obtained by apply | coating the precursor of an oxide semiconductor, The any one of Claims 1-9 characterized by the above-mentioned. Thin film transistor.   11. A method for producing a thin film transistor, comprising producing the thin film transistor according to any one of 1 to 10.

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